Some food for thought on the urban (suburban) vs. rural sustainability question - http://energybulletin.net/node/3757
There are pros and cons to living rurally vs. "in town". My biggest concern is dependence on automobiles. If you need to drive (to work, school, the store, etc.) on a daily basis then I don't think your location is very sustainable.
I think finding the right community of people is very important and that can happen either in a city or in the country.